1. Field of the Invention
The present invention relates to a semiconductor manufacturing apparatus to be used for forming a thin film on a surface of a workpiece or for etching a surface of a workpiece, and more particularly to a plasma processing apparatus for processing a surface of a workpiece having a deep groove or hole which is very small in dimension and high in an aspect ratio.
2. Description of the Related Art
Conventionally, a plasma processing apparatus utilizing a plasma has often been used as a processing apparatus for forming a thin film onto a fine pattern formed over a surface of an object to be processed such as a workpiece, for example, a substrate or a semiconductor wafer (hereinafter referred to as a xe2x80x9cwaferxe2x80x9d) or for performing fine processing of a surface of a workpiece. One or more processing gases are introduced into a processing chamber of the plasma processing apparatus, thereby generating a plasma. Consequently, some ions (reactive ions) and neutral particles (neutral radicals) contributing to the reaction are generated in the plasma. The ions are accelerated by the sheath on the surface of the workpiece and reach the surface of the workpiece, thereby contributing to the processing of the surface of the workpiece. The neutral radicals are transported to the surface of the workpiece by diffusion and deposit on the surface of the workpiece which contributes to the surface processing of the workpiece by performing a surface reaction or a reaction by the aid of the energy of ions incident on the surface.
For a method for forming a thin film on a surface of a deep groove or hole which is very small in dimension and high in an aspect ratio, molecular structures of a raw material for CVD (chemical vapor deposition) gas have been conventionally devised. Consequently, step coverage on a pattern surface has been improved and the formation of a thin film on a pattern having a high aspect ratio has been implemented.
On the other hand, as a method for performing fine processing of, for example, a deep groove or hole which is very small in dimension and high in an aspect ratio, there is a method for increasing the energy of ions incident on the surface of a workpiece. By this method, workability in the direction perpendicular to the surface of the workpiece has been improved and a pattern having a high aspect ratio has been formed.
However, as an aspect ratio of a pattern more increases, it becomes more difficult to process the surface thereof according to the conventional method.
In order to solve the above mentioned problem, several methods were proposed, which prevent the reaction by ions incident on a side wall of a pattern in plasma etching. For example, a method for forming an inhibitor layer on the side wall of the pattern, which layer protects the surface from the reactive species, is described in xe2x80x9cExtended Abstracts of Solid State Devices and Materials, p 229 (1986)xe2x80x9d; a method for reducing the temperature of a workpiece is described in xe2x80x9cAppl. Phys. Lett., 52, 616 (1988)xe2x80x9d; and a method for decreasing a gas pressure is described in xe2x80x9cJpn. J. Appl. Phys., 29, 792 (1990)xe2x80x9d.
However, even if these methods are used, an incident flux of the neutral radicals into a pattern having a high aspect ratio decreases during etching of the pattern having a high aspect ratio. In some cases, therefore, the inhibitor layer formed on the side wall of the pattern became thin, so that etching by ions incident on the side wall of the pattern could not be prevented.
Moreover, Japanese Patent Kokai Publication No. 163465/1994 has proposed a method for supplying a sufficient amount of neutral radicals to a pattern bottom by separating a processing chamber from a plasma chamber, and keeping the gas pressure within the plasma chamber higher than that of the processing chamber to provide the neutral radicals and gas molecules with a kinetic energy in the direction to the substrate and to enhance the incident directivity of the neutral radicals being supplied.
According to the above mentioned method, a unit construction is proposed to produce the pressure difference between the plasma generating chamber and the processing chamber, wherein a porous plate having holes of small diameters (which are not more than 3 mm) is provided and a plurality of turbo molecule pumps are provided so that gas within the processing chamber is exhausted at a total exhausting rate of 4000 litters/sec. However, in addition to an increase in the size of the apparatus, it is difficult for ions to transport to the processing chamber due to the small diameters of the holes, and ions are confined within the plasma generating chamber. Therefore, a plasma density within the processing chamber or an incident ion flux onto the workpiece becomes insufficient for processing the workpiece. In the case where an oxide film etching of a pattern having a high aspect ratio is carried out, there was a problem that an etch rate rapidly decreases due to the insufficient incident ion flux, so that through-put is reduced. In other words, although the neutral radicals are easily incident on the bottom portion of the pattern having a high aspect ratio by the porous plate provided to enhance the incidence directivity of the neutral radicals, the ion flux transported to the processing chamber decreases. As a result of the decrease of the ion flux, ions contributing to the etching reaction become poor so that the etch rate is depressed. The above mentioned method may be considered to be effective in etching reaction of silicon or organic materials in which neutral radicals mainly contribute to the reaction, however it is not suitable for etching of oxide film in which ions mainly contribute to the reaction. Further, the neutral radicals pass through the porous plate more easily than the ions since the formers are not affected by the sheath, however, they have a limited lifetime since they easily recombine with other molecules to be changed into other kinds of molecules or readily deposit on the wall of an apparatus. According to the above mentioned method, even if the neutral particles easily reach the bottom portion of the pattern having a high aspect ratio, most of the neutral radicals deposit on the surface of the plasma generating chamber or the number thereof decreases within the plasma generating chamber, so that the flux of the neutral radical incident on the workpiece is not so large. Therefore, it was difficult to enhance an etch rate even in which the neutral radicals mainly contribute to the reaction.
In order to solve the above mentioned problems of the prior art, it is an object of the present invention to provide a plasma processing apparatus capable of forming a thin film over a groove or hole which is very small in dimension and high in an aspect ratio at a high rate or forming a pattern with high precision at a high etch rate.
A first aspect of the present invention is directed to a plasma processing apparatus which comprises a processing chamber, processing gas supply means for supplying one or more processing gases into the processing chamber, plasma generating means for changing the processing gases supplied into the processing chamber to a plasma, a mounting stage for mounting an object to be processed which is provided in the processing chamber, bias applying means for applying an electrical bias voltage to the mounting stage, a gas storage chamber which is placed at a position opposite to a face of the mounting stage (on which the object being processed is mounting) and which is provided with a supply system for supplying neutral particles or one or more gases to generate the neutral particles, a partition plate which separates the gas storage chamber from the processing chamber and having jet holes for jetting the neutral particles into the processing chamber, and an exhaust system.
A second aspect of the present invention is directed to the plasma processing apparatus according to the first aspect of the present invention, wherein the partition plate is a counter electrode which is placed in a position opposite to a face of the mounting stage.
A third aspect of the present invention is directed to the plasma processing apparatus according to the second aspect of the present invention, wherein the partition plate comprises a dielectric film formed on an electric conductor.
A fourth aspect of the present invention is directed to the plasma processing apparatus according to the second aspect of the present invention wherein the partition plate is grounded.
A fifth aspect of the present invention is directed to the plasma processing apparatus according to the second aspect of the present invention wherein the partition plate is provided with a power supply for applying a radio frequency or a DC bias voltage.
A sixth aspect of the present invention is directed to the plasma processing apparatus according to the first aspect of the present invention wherein each jet hole is in a shape of a nozzle having an enlarged size (or diameter) toward the side of the processing chamber.
A seventh aspect of the present invention is directed to the plasma processing apparatus according to the first aspect of the present invention wherein the gas storage chamber is composed of a plurality of discrete gas storage chambers and a plurality of partition plates.
An eighth aspect of the present invention is directed to the plasma processing apparatus according to the first aspect of the present invention wherein the gas storage chamber is provided with plasma generating means.
A ninth aspect of the present invention is directed to the plasma processing apparatus according to the first aspect of the present invention wherein the gas storage chamber is provided with a radical source.
A tenth aspect of the present invention is directed to the plasma processing apparatus according to the first aspect of the present invention wherein the gas storage chamber is provided with an ion source.
An eleventh aspect of the present invention is directed to the plasma processing apparatus according to the tenth aspect of the present invention wherein the ion source is provided with ion accelerating means.
A twelfth aspect of the present invention is directed to the plasma processing apparatus according to the first aspect of the present invention wherein a diameter of the jet hole is smaller than a mean free path of neutral particles in the gas storage chamber.
A thirteenth aspect of the present invention is directed to the plasma processing apparatus according to the first aspect of the present invention wherein a longitudinal length of the jet hole is longer than a mean free path of the neutral particles in the gas storage chamber.
A fourteenth aspect of the present invention is directed to the plasma processing apparatus according to the first aspect of the present invention wherein a pressure within the processing chamber is lower than that of the gas storage chamber.
A fifteenth aspect of the present invention is directed to the plasma processing apparatus according to the first aspect of the present invention wherein a distance between the mounting stage and the partition plate is not longer than a mean free path of the neutral particles in the processing chamber.
A sixteenth aspect of the present invention is directed to the plasma processing apparatus according to the first aspect of the present invention wherein the supply system is provided with pulse valve supply means.
According to the first aspect of the present invention as described above, since the plasma processing apparatus comprises the processing chamber, the processing gas supply means for supplying the processing gases into the processing chamber, the plasma generating means for changing the processing gases supplied into the processing chamber to the plasma, the mounting stage for mounting an object to be processed which is provided in the processing chamber, bias applying means for applying the electrical bias to the mounting stage, the gas storage chamber which is placed at a position opposite to the face of the mounting stage for mounting the object being processed and which is provided with the supply system for supplying the neutral particles or the gases to generate the neutral particles, the partition plate which separates the gas storage chamber from the processing chamber and having the jet holes for jetting the neutral particles into the processing chamber, and the exhaust system, it is possible to perform, at a high processing rate, the surface processing of the workpiece having the patterns which includes a deep groove and/or hole which is very small in dimension and high in an aspect ratio.
According to the second aspect of the present invention wherein the partition plate is arranged to be the counter electrode to the mounting stage in the first aspect, the processing for the workpiece can be uniformly performed.
According to the third aspect of the present invention wherein the partition plate comprises the dielectric film formed on the electric conductive material in the second aspect, it is possible to obtain an effect that deterioration in the partition plate is prevented.
According to the fourth aspect of the present invention wherein the partition plate is grounded in the second aspect, a uniform processing of the workpiece can be carried out.
According to the fifth aspect of the present invention wherein the partition plate includes the power supply for applying the radio frequency or the DC bias voltage in the second aspect, the density of particular particles in the processing chamber can be adjusted by the selection of the material of the partition plate and/or the control of the electric potential of the partition plate. As a result, the processing conditions can be flexible.
According to the sixth aspect of the present invention, wherein each jet hole or port is formed in the shape of a nozzle having the enlarged diameter at the side of the processing chamber in the first aspect, the particles in the gas storage chamber can be jetted into the processing chamber without reducing a transport speed thereof during the passage through the jet hole.
According to the seventh aspect of the present invention wherein the gas storage chamber is constituted by a plurality of gas storage chambers and a plurality of partition plates in the first aspect, particle flows can be uniformly supplied to the workpiece and the processing for the workpiece can be uniformly carried out. Moreover, it is also possible to vary the processing of the workpiece in its face by changing the particles to be introduced.
According to the eighth aspect of-the present invention wherein the gas storage chamber includes the plasma generating means in the first aspect, the plasma can be generated at a lower pressure than in the conventional case, and the ions and/or neutral particles can be incident on the workpiece without collision or with a few collisions, and thus, anisotropy for processed profile can be enhanced. Moreover, a particular kind of the neutral radicals can be introduced into the processing chamber in a large number by adjusting the operating pressure and/or the source power of the plasma generating means which are provided in the gas storage chamber. As a result, the neutral radicals suitable for the intended processing can be supplied to the workpiece and the processing can be improved.
According to the ninth aspect of the present invention wherein the gas storage chamber includes the radical source in the first aspect, a large number of the neutral radicals suitable for the intended processing can be introduced into the processing chamber, so that the processing performance can be enhanced.
According to the tenth aspect of the present invention wherein the gas storage chamber includes the ion source in the first aspect, a large number of ions suitable for the intended processing can be supplied into the processing chamber, so that the processing performance can be enhanced.
According to the eleventh aspect of the present invention wherein the ion source is provided with the ion accelerating means in the tenth aspect, the neutral particles having an energy suitable for the intended processing can be supplied into the processing chamber in a large number, so that the processing performance can be enhanced.
According to the twelfth aspect of the present invention wherein the diameter of the jet hole is smaller than the mean free path of neutral particles in the gas storage chamber in the first aspect, a neutral particle flow which has a particular ratio of a temperature in a vertical direction to a temperature in a horizontal direction with respect to the workpiece face can be supplied to the workpiece.
According to the thirteenth aspect of the present invention wherein the length of the jet hole is greater than the mean free path of the neutral particles in the gas storage chamber in the first aspect, a neutral particle flow which has a particular ratio of a temperature in a vertical direction to a temperature in a horizontal direction with respect to the workpiece face can be supplied to the workpiece.
According to the fourteenth aspect of the present invention wherein the pressure of the processing chamber is lower than that of the gas storage chamber in the first aspect, when the neutral particles are to be jetted from the gas storage chamber to the processing chamber through the jet holes, a kinetic energy is given to the particles in the direction perpendicular to the workpiece face, so that the temperature in the direction perpendicular to the workpiece face can be raised. Thus, the temperature of the neutral particles in the direction perpendicular to the workpiece face becomes higher than the temperature in the horizontal direction, the neutral particles can easily be supplied to the bottom portion of the pattern having a high aspect ratio.
According to the fifteenth aspect of the present invention wherein the distance between the mounting stage and the partition plate is not longer than the mean free path of the neutral particles in the processing chamber in the first aspect, the neutral particles jetted from the gas storage chamber can be supplied to the surface of the workpiece without rescattering in the processing chamber.
According to the sixteenth aspect of the present invention wherein the supply system is provided with pulse valve supply means in the first aspect, the difference in the pressure between the gas storage chamber and the processing chamber greatly increases. Accordingly, the neutral particles or ions can be sufficiently supplied to the bottom portion of the pattern having a high aspect ratio.